As 2025 ends, the starry stonewort situation on Middle Cullen remains a significant concern.

That’s because the infestation – which was about one-acre when first discovered in May 2024 and grew to about three acres by spring of 2025 – has spread to about six acres.

This new size estimate is based on a Scuba diving perimeter survey conducted in mid-October by PLM, the algaecide applicator the Cullen Lakes Association hired for the fourth and final chemical treatment to kill and contain this stubborn and unwanted lake invader.

According to PLM, much of this spring’s three-acre infestation has been burned down and “shattered” by four treatments of Komeen Descend, a DNR-approved liquid herbicide and algaecide that uses copper ethylenediamine to control starry stonewort. Previously, stonewort grew as tall as six feet up from the bottom. Today, most of that growth has been flattened.

Unfortunately, small and sporadic new infestations have taken root nearby, most toward the western shore across and down from the public boat launching site. Some of this “new growth” is growing in eight to 10 feet of water. The sporadic parcels are about the size of a four-by-eight sheet of plywood.

The discovery of new growth outside the perimeter of the 2025 chemical treatment area is discouraging. It was hoped that by hitting the infestation hard with aggressive and repeated algaecide applications we could contain the infestation. That doesn’t seem to be the case.

However, PLM said the huge reduction in stonewort biomass in the three-acre treatment area is encouraging. It is too early to tell what effect the 2025 applications will have on next year’s growth but hopefully our October treatment – timed to prevent the algae from building energy stores heading into the winter – will generate positive results.